Boundary lines represent boundary markers in the form of objects or lines to divide a corresponding road into plural parts as lanes. For example, they consist of solid or dashed white painted lines placed on the corresponding road along each lane thereof, or consist of raised markers placed on the corresponding road intermittently along each lane thereof. Thus, in order to improve the running safety of motor vehicles, it is important for the motor vehicles in running one lane of a road ahead thereof to accurately recognize the boundary lines formed on the road.
In view of the circumstances, boundary line detection systems are installed in motor vehicles. Such a boundary line detection system installed in a motor vehicle picks up an image (a road image) of a region including a road (road surface) ahead of the motor vehicle, and subjects the road image to image processing to thereby extract edge points indicative of painted white lines and/or raised markers. In addition, the boundary line detection system detects boundary lines on the road based on the edge points. One of these boundary line detection systems is disclosed in Japanese Patent Application Publication No. 2007-141052.
Boundary lines to be detected by a boundary line detection system are used, in combination of information indicative of the behavior of a corresponding vehicle, such as its travelling direction, travelling speed, and/or steering angle, for prediction of whether a corresponding vehicle will depart from a corresponding lane and/or for automatic control of steering wheel.